Hydraulic transmission



4 Sheets-Sheet l E. K. BENEDEK HYDRAULIC TRANSMISSION Filed Feb. 7, 1955Sept. 16, 1941.

@ATTORNEY.

- Sept. 16, 1941. E EN DEK 2,255,963

' HYDRAULIC TRANSMISSION Filed Feb, '7, 1955 4 Sheets-Sheet 3 INVENTOR.ELEK KEJENEDEK- ATTORNEY.

p 16, 1941- E. K. BENED EK 2,255,963

HYDRAULI C TRANSMISS ION Filed Feb. 7, 1935 4 Sheets -Sheet 4 EELS- E 25a 46 ny 2; 5

INVENTOR I I I JBK KEIENED BK Patented Sept. 16, 1941 1 UNITED STATE 5*PATENT OFFICE nymmuuc raassmssron Elek K. Benedek, Bucyrus, OhioApplication February '1, weasel-rel No. 5,429

"This invention relates to hydraulic variable speed transmissions andparticularly to that type translated. by a rotary, radial piston,positive displacement fluid pump into the fluid pressure which, in turn,is passed to a cooperating rotary, radial piston, positive displacementhydraulic motor wherein it is retranslated into torque output for finalutilization. Hydraulic transmissions of this general type heretoforeknown have not met with extensive acceptance in the trade :due primarilyto certain imperfections and disadvantages inherent in the particularstructures and designs employed. Chief among these disadvantages are thelow efiiciency of output relaof transmission in which the power input is4 Claims. (CI. 60-53) direction while maintaining a high efliciencythroughout the range of operation.

Still another object is to provide a draulically interlocked duringrotation as a result of which neither leads nor lags with'respect v tothe other but, on the contrary, any change in the operation of one isimmediately reflected in the other.

Another object is to reduce the number of working parts by utilizingcertain necessary parts tive to input and the limited range of speed,

power and-torque ratio.

One of the principal objects of the present invention is to provideagreatly simplified transmission of this type in'which substantiallymechanical and hydrostatic balances are maintained throughout and inwhich the various working parts are substantially symmetrically arrangedwith respect to each otheru An equally important object is to provide ahydraulic transmission in which the pump and motorhave the same flowcharacteristics, as a result of which shockless' fluid communicationbetween the pump and motor is obtained, that is, the pump and motor havethe same general in new relations to each other to perform func-. tionsin addition .to those functions 'for which such parts have been usedheretofore.

Still another object is to provide a transmission having a pump andmotor so connected together operatively as to. maintain a betterhydrostatic balance between thetwo and between 1 their respective,working parts and thereby to retrolled independently of each other sothat a much-wider range of speeds and torque transstructure so that theresultant flow, velocity and flow acceleration betweenthe pump andpintle portsis such thatno pressure impulses are developed between thepump and motor ports in the 1 v 'of which are of the reversible variabledisplacepintle during operation.

A correlative object is to provide in e hydraulic" transmission apumpumd a motor such that the motor accommodates exactly the fluiddelivered by the pump; receiving the fluid 'in the same manner as topath,'velocity, and acceleration as delivered by the pump instead of atadifie'rent rate which would result in entrapment of the fluid in themain pintle passagesconnecting the pump and motor.

Another object is to provide a and more highly efiicient fluid circuitin 'a'tr'ansmissidnof this character.

Still another object mission and combinations of speed and torque forany given power input can be obtained.

A, more specific object is to provide in a hydraulic transmission a pumpand a motor both ment type in'which-the stroke changing mechanisms, andtherefore the control of flnal delivery. of each may beoperatedindependently of the other. a

10 Another object is to provide a dual stroke.

changing mechanism for a pump and motor combination of this characterwhichcooperates with the two in a manner to coordinatethe strokechanging mechanism or one with respect to the other so that a very widerange of speeds and K torquenecessary in connection with many inis toprovide in ahydraulic transmission a completely anti-friction pump anda-completely anti-friction motor so connected in the circuit thatf orany given delivery of the pump, the motor may be operated from maximumstroke in one'dire'ction entirely to the zero .dustrial machines may beprovided easily and efliciently', by conveniently arranged adjustmentreadily accessible to and operable by the operator of the particularmachine. 4

Having in mind the problems' presented and conditions to be metin thepractical field, other advantages in connection with this inventioninclude a transmission by which a commercial, stroke and to maximumstroke in the reverse an e of sp ed r i between the te f the closedcircuit by which the pump and motor are hycommercial utility. V in thecomparatively small overall size required which has been reduced about50% over prior pletely reversible.

sha'ftof the power input mechanism shaft the speed of the shaft of themotor of the transmission may be obtainedwith a single stage unit whilemaintaining an overall efllciency of transmission of from 80 to 95%,depending on the size of the transmission. By commercial range is meantthe range of speeds required by general Another advantage residesmechanical gear transmissions.

Other objects and advantages will become apparent from the followingspecification wherein reference is made to the drawings in which- Fig. 1is a horizontal longitudinal sectional view of a hydraulic transmissionmechanism embodying the principles of the present invention and is taken.on a horizontal plane through the axis of rotation, as indicated by thelines l--l in Figs. 2 and 3, the spider of the partition wall and thepintle-being shown cleamess;

- Figs. 2 and 3 are vertical cross sectional views.

of the pump and motor respectively of Fig. 1 and are taken on planesindicated by the lines 2-2 and 3-3 respectively of Fig. 1; c

Fig. 4 is a vertical cross sectional view of the and in plan view forpurposes of p transmission taken on a plane indicated by the line 4-4 ofFi 1;

Fig. 5 is a horizontal sectional view of a coordinating controlmechanism for adjusting the speed. and torque delivery of thetransmission;

Fig. 6 is-a vertical sectional view of a portion of the pump rotor andpintle and is taken on a plane indicated by the line S-B of Fig. l; and

:Fig. 7 is a vertical cross sectional view taken on a plane indicated bythe line 'I-"I in Fig. 5.

Fig. 8 is. a diagrammatic illustration of the fluid circuit of thepresent transmission.

Referringparticularlyto Fig. l, the transmission is mounted in a bodycomprising a casing l, closed at the ends by rigid load and thrustsupporting cover plates 2 and 3 respectively.

Mounted within the body near one end thereof is a puinp rotor 5 of therotary radial piston type. Rotatably mounted near the opposite end ofthe body is a rotor 6 which also is the rotary;

radial piston "type and, in fact, except for its larger size, is asubstantial duplicate of the pump rotor 5. Accordingly, therefore, onlythe rotor 5 be described in detail. It should be noted thatIthedesignations of the rotor 5 as the pump rotor and the rotor 6 as themotor rotor are primarily-for convenience in description as either maycomprise the pump and the other correspondingly comprise the motor, bothbeing com- The rotor 5 comprises a rigid radially extendmit any axialthrusts on the rotor into the bearings. It should be noted that the setsofbearings at the respective ends of the rotor are spaced longitudinallyof the rotor equidistant from the'plane of the cylinder axes so as tomaintain as effective mechanical balance of the rotor as is practicable.The outer race of the sets of bearings I3 at the end of the rotoradjacent the cover 2 is securely mounted in an internal.

annular recess in the cover2 to transmit directly to the cover any axialoutward thrusts and radial thrust of the motor. At the opposite or innerend of the rotor 5, within the body, is a rigid partition or supportingwall I5,=integral with or fixedly secured within the casing l. by radialspider arms IS. The supporting wall l5 terminates longitudinally closeto the adjacent end of the retor body and is provided with an internalannular recess ll corresponding to and coaxial with the recess in thecover 2 for receiving the outer race a of the set of bearings I 3 at theinner end of the rotor and for supporting the .rotor at its inner endagainst axial thrust and radial thrusts. It should be noted that boththe bearing races l2 and; their complementary. outer races are sogrooved astc transmit axial thrusts from the rotor 5 through the racesand the bearings l3 to the end cover 2 and supporting wall I5respectively.

Carried by the rotor, in the cylinders 8, are a v plurality of radialpistons 2li each of which is connected through the medium of acrosshead' The secondary rotor 22 is supported within the body I throughthe medium of anti-friction bearings 23 and a surrounding annularreactance housing 24. The secondary rotor 22 and the re- 3 actancehousing 24 are coaxial with respect to each other and the housing 24, inturn, is mounted in suitable guideways, shown in Fig. 2, in the body Isoas to support'and maintain the secondary rotor with its axis' parallelto the axis of the primary rotor while permitting shifting of thesecondary rotor and its housing to change the relative eccentricity ofthe primary and seconding body portion I in which is provided a seriesof radial circumferentially spaced piston cylinders 8, each of whichcylinders has a radial valve port 9 opening into an axial bore III ofthe rotor, later to be described. The rotor-is provided at each end ofthe body portion 1 with annular hubs j l, the hubshaving axial annularfaces which re- "ceive the inner races i2 of anti-friction bearings I3,the hubs being coaxial and of the same external diameter so that thebearing sets respective thereto shall -be 'coaxial' with the rotor witha radial flange I05 in the plane and the same distance radially from therotor axis of rotation.

. The body portion 1 of the rotor 5 is provided with radially extendingannular shoulders adjacent each hub which shoulders may engage theinner'edges of the bearing races I! so asto-transary rotors and therebyvary the length of stroke of the pistons. The sets of bearings 23 arepreferably spaced equidistant from each other at opposite sides of theplane of the piston axes.

The space between the sets of bearings is occupied partially by theheads of the. pistons during reciprocation thereof, and is open topermit lubricant introduced through the housing 24 to pass to thebearings 23, the parts of the piston assemblages, and the needlebearings of the pistons. The shifting of the secondary rotor and housing24 maybe accomplished through the medium of any suitable control means,for example, control rods 25, later to be described in detail, throughwhich lubricant may be introduced through the housing wall. The rotor5'is provided of the cylinders 8, the flange having radial guideways I06in which crossheads I20 of the pistons 20 are reciprocable. Thecrosspins 2| of the pistons are mounted in the piston crossheads [20 oncapillary March 16, 1937.

cageiess needle rollers. such as described in my United States LettersPatent No. 2,074,202, issued The halves of the rotor 22 are connectedtogether by bolts 13! on which' are carried sleeve spacers I23 which spacethe halves a proper dis- Y tanc'e apart from each other. Suitableopenings III are provided in the flange "I for accommodating the sleevespacers I23 and the bolts III.- The openings l2! are of proper diameterso that ranged to transmit radial thrusts and axial-loads to the rigidfixed portions of the body. Consequently, the primary and secondaryrotors and the spacers engage the peripheral walls thereof H at maximumstroke setting of the rotor 22 and thus transmit torque between therotors at maximum. stroke position.

The rotor 3 carries at its outer end an impeller shaft 33 which extendsthrough the end cover 2 of the body of the transmission and ispreferably integral with the corresponding end of the rotor I. Therotor, as previously mentioned, is pro- 'vided with an axial, dead end,pintle receiving bore III which extends from the end of the rotoradjacent the supporting wall ll axially beyond the piston cylinders 3and close to the plane of the outer set of bearings l3.

Fixedly mounted withinthe wall- I! by press a fitting and coaxial withthe bore l3 and protruding thereinto is one end of a valve pintle 3|which, in the zone of the valve ports 3 of the bore leis hydraulicallyfitted to the complementary walls of the bore l3. The pintle 3| has theusual valve portion with reversible ports 32 and 33' positioned axiallyto cooperate with the ports 0 of piston assemblages and pintle maycooperate. in

such a manner that substantially all of the torque transmitted to therotor through the im-' .peller shaft 30 is translated into hydrostatic;

pressure and no material portion thereof is misapplied or wasted increating stresses and bending moments between the primary rotor and thepintle or between the working parts of the rotors and cooperating pistonassemblages. Furthermore, since all thrusts are directly resisted bybalanced anti-friction means, no excessive frictional resistance betweencooperating surfaces is 7 developed.

' Referring, next briefly to the motor of the transmission,'the rotor 8is mounted at one end in the portion of the wall I! opposite to thatsupporting the rotor I, and at its outer end'in the end cover. 3, setsof anti-friction bearings 38 cooperating with the wall I5 and end cover3 respectively and with the rotor 6 in thesame manner as the bearings i3cooperate with the primary rotor I being provided. The-motor rotor 6also .has a plurality of radial piston cylinders 40 in which are mountedradial pistons 42 cooperable with a secondary rotor N in the same manneras the pistons 20 and rotor 22. The secondary rotor,

in turn, is mounted in an annular reaction housing 44 corresponding tothe housing of the primary rotor. The secondary rotor housing M is theprimary rotor 5 consequent upon rotation of the rotor. The pintle 3|terminates in spaced relation to the dead end of the bore ll of therotor, as indicated at 34, for purposes later to be described. v

Adjacent its free end, the pintle is provided with an annularaxiallyextending groove denning a bearing race which accommodatesantifriction capillary needle bearings 35, the wall portion of the borel3 overlying the bearings 38 forming e complementary race for the needlebearings 5; At the portion of the pintle adjacent the wall it andpreferably in the same zone. axially of the pintle as the bearings l3,the pintle is provided with another axially extending annular surfaceforming a bearing race for a set of capillary needle bearings 38. At theend of the "rotor bore [0, adjacent this portionofthe pintle,

the bore I0 is counterbored toa slightly larger diameter, the wall ofthe counterbore providing the external bearing race of the bearings 3G.The portion of the pintle forming the race for the bearings 38 is ofgreater diameter than the valve portion of the pintle andthereby forms a,the greater rigidity afforded by its heavy shank and at the same timethe hydrostatic load is transferred to the bearings 33 and 38 andtherethrough to the rotor mountings and to the body of the transmission.This oounterbore, indicated the valve portion of the pin-.

mounted in the body of the transmission so that it may be shifted in thesame manner as. the V a housing 24 for varying the relative eccentricityof.

the primary and secondary rotors of the motor while maintaining theiraxes in parallel relation. For this purpose, a rod 45, corresponding inform and function to the rod 25, is connectedwith the secondary rotor"44 and extends through the adjacent wallof the casing I.

The mountings and corresponding parts of the rotor i are likewisesymmetrically disposed with respect to' the plane of its piston axes.The rotor 6, in turn, is provided with a dead end axial bore 41. Itshould. be noted that the pump .rotor i and the. motorrotor 8 are-somounted with respect to each other that the respective dead end axialbores Ill and 41 thereof are coaxial with respect toeach other and havetheir open ends to.-

ward and adjacent the wall It. Contraryto the usualpractice, a separatepintle eccentric to the pump pintle is not provided for the rotors. ,In-

stead, the pintle 3| which is mounted fixedly at its midportiqn in thewall it, protrudes from this mounting not only into the bore ll of thepump rotor but correspondingly, from the opposite face of its s'uportingwall, into the bore 41 of the at-3l, is of suflicient length to permitaxial clear ance between its inner end wall and the shank' portion ofthe pintle.

By this arrangement of the pintle; the needle bearings 35 and" 3', thebearings l3, and-bearings 23 are balanced and symmetrically arrangedwith respect to the plane of the piston axes and armotor rotor. Thelatter protruding end of the pintle is mounted in the'bore 41 andcooperates with the ports of the piston cylinders 40 of the rotor 6through reversible ports 43 and '49 in the same manner as the oppositeend cooperates with thj'ecylinder ports of the primary rotor. As in the.case of the former, the motor and of the pintle likewise has a valveportion hydraulically I fitting a corresponding portion of thebore "andterminates in spaced relation to the dead end of the rotor bore.

The rotor i carries an" axially extending torque delivery shaft 5| ofthe transmission, the shaft 5| preferably being integral with the. rotor6 and extending therefrom through the end cover 3 of v the transmission.Insofar as the sizes of the to E tors 5 and 6 permit they are balancednot only sioned will readily be supplied through the valve 61 and anyslip' fluid in the body subsequently maybe drained from the body throughthe me-' dium of the plugs in the lustrated in Figs. 2 and 3.

As more fully explained in my'copending application, Serial No. 754,753,filed November 26,

bottom wall thereof, 11-

1934, now Patent 2,126,722, dated August 16, 1938, I

it is'desirable to maintain as near as possible not only hydrostaticbalance of the pintle 3| but also, to efiect proper lubrication of thebearings IS in' which the pintle is mounted is provided 1 with a radialbore 55 and-a communicating coaxial enlarged counterbore' 56. Atthejuncture .of the bores 55 and 56, a valve seat is formed on which isseated a relief valve plug 51"which, through the medium of a forcedirecting head 58, is held firmly in place by a compression spring 59 ofpredetermined strength. The outer end of the bore 56 is sealed by asuitable screw plug 60 against which the end of'the, spring 59 abuts.Extending laterally from the bore 56 are discharge ducts 61 whichcommunicate with the interior of the body of thertransmission mechaenism.

' The pintle is provided with the customary longitudinally boredpassages or ducts 32 and 63, the former of which communicatewith thepintle inlet ports 32 .at the pump end of the pintle and with the pintledischarge ports 43 at the motor end of the pintle thus forming thepressure circuit between the pump and motor. The ducts 63 communicatewith the pintle ducts 33 and 49 to form the suction' circuit between themotor and pump. That portion of the pintle mounted in the wall 15' isprovided with a relief port 64 which communicates with the pressureducts 6,2 of the pintle and, in turn, communicates with the duct orradial bore 55. Consequently, in event. an undue or excessivehydrostatic pressure is created in the transmission be yond that pointallowed for safety of the transmission or of a machine .tool.beingdriven thereby, the valve 51 will be unseated thereby and relievethe pressurethrough the medium of the ducts 6| into the interior of thebody which provides the fluid sump, designated S in Fig. 8. The

between the pintle and rotor.- By terminating the pintle in spacedrelation to the ends'of the bores l0 and 41, as indicated at 34 andrespectively, and by introducing fluid thereinto at operating pressureof theg'transmission, this may be accomplished. In the present instancethis is especially desirable due to the fact that a common pintle isprovided and any tendency of it to shift, due to h'igh fluid pressure atits ends, would effect an unbalance and ineflicient operation of boththe pump and motor. The diameters of the respective ends of the pintleare substantially equal. Therefore, if fluid from the pump under thesame line pressure is delivered either in the form of slip fluid orthrough the ends of the passages -62'into the dead ends of the bores I 0and 41 respectively, as indicated at 34 and 50, the total hydraulicreactionon one e d of the pintle will be substantially equal to. thetotal hydraulic reaction on the other end and, since these hydraulicreactions will thus be substantially balanced, there is no tendency forthe pintle to be shifted axially by an unbalanced totalhydraulicpressure. For insuring the same hydrostatic pressure at both ends andpermitting it to be discharged as a continuous annular stream over theneedle bearings at the respective ends of the pintle, the pressureducts'62 of the pintle extend beyond their pintle ports 3? and 48 andentirely through the pintle, opening in the ends of the pintle so as todischarge into the dead ends of the bores l0 and. 41 respectively. Thesuction pressure which is desired as maximum for anyv circumstances canbe obtained by changing the pintle is a main supply duct or radial bore6-5 compression of the spring 59 or changing the spring itself. v j

Correspondingly, in the sameportionof the or nonpressu're ports 63 aresealed at the ends, as better illustrated in Fig. 6,.so that the fluidintroduced to the respective rotor bores at the ends of the pintle isnot only in hydrostatic ban ance but'is at exactly the same pressure asthat maintained for operation of the motor. Any hy-e drostaticreactance' on the rotors at the ends of the bores are resisted by therotor bearing and the body of the transmission.

The-radial and axial hydrostatic balanceis .made possible by thecombination of a pump in the wall 15 may communicate with a suitablefluid sump or sourceof supply of fluid. A light check valve 61 operableto admit fluid into thebore and to prevent discharge therefrom whenpressure is created in such passage is operatively disposed intermediatethe bore and the sump. It is apparent therefore that when the p'umpisoperating, fluid -is delivered under pressure through the ports 32 bythe pistons 20 and passes through ducts 62 and the ports to the motorwherein it may cooperate with the pistons 42 thereof to drive the motor.

When the motor 'pistons are brought into alignment with the pintle ports49, in turn, the fluid is exhausted therefrom under a slight pressureand passes throughthe ducts 63 into the pintle suction or dischargeports 33 at the pump end of the pintle, a full supply of fluid in thecircuit being assured by the check valve 61. The

I slight leakage or slip of fluid necessarily occaand'a motor in areversible hydraulic transmission in a one way circuit wherein the pumpoperates for one way delivery and the motor is freely reversible, aswil1 later be described in connection with the hydraulic circuit.

As previously described, the secondary rotor housings 24 and 44 of thepump and motor respectively are shiftable for varying the relativeeccentricity of the corresponding primary and secondary rotors, thisshifting being accomplished through the-medium of control rods 25 and 45respectively. In some instances it is desirable-to adjust the speedratio and torque de-' sired by shifting the respective reactance hous-'ings concurrently in a predetermined relation to each other during theoperation of a particular machine driven by the transmission or for aparticular kind of work. For example, as-

suming that the motor is set at a given eccentricity and theremaintained, the setting of a greater eccentricity on the Pump wouldprovide a larger flow of fluid but at lower pressure than would a lessereccentricity on the pump, the

latter-decreasing the volumetric discharge-of the pump .while increasingthe pressure. consequent-'- ly, by varying the eccentricity of the pumponly,

a high speed with a correspondingly-high'torque delivery of the motorcould not be obtained' Reversely, 'if the pump were driven atpredetermined adjusted eccentricity and the eccentricity of the motoradjusted, a greater eccentricity of the motor would produce a slowerspeed but a greater torque, while the lesser eccentricity on the motorwould produce a higher speed but lesser torque. It is apparent thereforethat if only one reactance means of the transmission is adjustable,increase in speed can be obtained only by a sacrifice in torque deliveryand conversely increase in torque delivery can be obtained only at asacrifice of speed even'within normal practical requirement ranges ofspeed and torque. however, an unlimited number of additional dif--ferent combinations are obtainable. For instance, 'a high speed and lowidling torque could 'be obtained by setting the pump at compara- Withboth reactances adjustable,

tively low eccentricity and the motor at a, very.

low eccentricity. For the same speed and concurrent higher torque, thepump could be set at a somewhat higher eccentricity and at the same timea much greater eccentricity provided at the motor, thus the loss inspeed for greater torque in the motor could be offset by the larger flowprovided from the pump. By increasing the eccentricity of either thepumpor motor reactance and decreasing the eccentricity'or the 'otherunit concurrentlyfa double acceleration or deceleration in speeddelivered by the motor is obtained and also high speed, low torque orlow speed, high torque'and an infinite number -of intermediatecombinations of speed and torque are available. These changes in speedand torque are effected by a continuous rise and fall instead of in thestep by step stage as in mechanical transmissions. The eccentricity ofthe pump and motor may be independently controlled by any suitablecontrol means. For purposes of il1us tration, however, and since withincertainlimits the combinations desired are well known and are keptduring the entire operation, it is desirable that a control means beprovided for coordinating the setting of the reactances. For the purposeof illustration, substantially duplicate hydraulically operated controlsare provided for the pump and motor, these controls being operativelyconnectedto each other so that they are operated from a common sourceand will" maintain predetermined relations between the eccentricities ofthe respective rotors. The principles of eachfcontrol are more fully setforth in my co-pending application, Serial No. 749,746,

axially and intermediate its ends is provided 'with 'a 1 suitable inletfrom a source of fluid under pressure, the fluid to be introduced intothe housing 18 at the midportion thereof through a port I3 and inalignment with an externalannular groove 16 on the piston head.- Thepiston head is provided with an axial bore. II with which communicate atlongitudinally spaced points ducts l8 and 18 or the*piston head, theduct 18. opening at one end of the piston into the cyl- 'inder housing10 and the duct 18 opening through the other end of the piston head intothe housing 1 10. In addition aplurality of ducts 88 communicate withthe groove 18 and with the bore 11 ofthe piston for transmitting fluidunder pressure thereinto. Disposed in and reciprocable longitudinaliyalong the bore I1 is a pilot valve piston 8|, the pilot piston beingshiftable axially along the bore 11 through the medium of an operatingrod 82., The pilot valve is provided intermediate its ends with anelongated annular reduced portion so as to form with the wall or thebore 1'1 an annular pocket 83 positioned so as to always be incommunication with the ducts- 80. At the ends of and defining thisannular portion are enlarged valve portions 84. which,

when the pilot valve'is disposed in the intermediate position, blockthe. entrances ofthe ducts I8 and 18 respectively, However, when thepilot piston is shifted downwardly in Fig. 5, it is apparent that thecorresponding valve portion 84 thereof will move 'out of alignment withthe end of the duct 18 so as to permit-communication between the duct I8and the bore 11. Also-it will block thepassage of fluid from theannularchannel 81 into the duct 18 and into the end of the pilot piston bore 11adjacent the rod 25. At the'same .time, the other valve end will havepassed downwardly beyond the fpenin of the duct Ilinto the bore 11, soas o co eat this duct with the channel 88. Therefore fluid underpressure will pass from the channel 83 through the duct 18 into theupper end of the piston cylinder 10 while at the same time freedischarge of fluid from the cylinder/at the opposite end of the pistonsis provided through the duct 'I8 'and passage 11. Obviously therefore,the piston will be driven downwardly-by hydro-'- static pressure. If'thepilot piston 8| is shifted upwardly or in the opposite direction theduct 18 will be connected with the channel 83 so as filed October 24,1934, now Patent 2,111,659, dated March 22, 1938.

Referring more specifically to Figs. 1, 5 and 7-,

the transmission body is provided with housings Hi and II connectedtogether by a suitable flange 12, the housings each comprising hydrauliccylinders of one control unit, that for the pump being the housing Illand thatfor the motor being the housing ll. identical in form andoperation and vary only Since the controls are slightlyin size, thecontrol associated with the pump only will .be described in detail, thecorresponding parts of the control associated with the motor beingdesignated by corresponding primed numerals and not specificallydescribed.

to admit fluid under pressure thereinto for mov ing the piston head 18in, the opposite direction. In order. to vent the opposite side of thecylinder in such instance, a vent is provided in the pilot piston beyondthe adjacent valve portion 84 toward the rod 82,'this vent communicatingwith an aaial duct 88 in the pilot piston which n discharges into theduct or passage 1]. The vent 85 is so located relative to the pistonhead and pilot piston 8| that it is disconnected from any other ductsexcept in the position last described. Theoperation of the pilot controlis as follows. Upon movement of the rods 82 and 88, the pilotv valvepistons 81' and H are moved to formv a connection for admitting fluidunder pressure from the source of sup ly to the cylinders 18 and 1 whichmo v es the .pistons and until valve heads '94 and 84' close of! thepassages II the and'lland the passages 19' and "l9" respectively.

plntle. Sincethe valve 5] is closed except. for

unusual pressures which may be inadvertently Accordingly,'the movementof the rods and in each direction andconsequently the movement of thereactance housing 24 and 44 will be proportional to the adjustment orsetting-of the I end portion 81 is provided with an axial duct,

as illustrated, which communicates with the pas-2 sage 'Il a'ndopen atits opposite end. Thus all hydraulic fluid bled into the passage ll willbe discharged into the interior of the 'body I and; in the formillustrated, through the reactance housing 24 onto the. pistons 20, thebeari'ngs 23, the bearings of the piston crosspin 'II' developed andsince the valve 61 opens only to admit replacement fluid from the bodywhich provides a sump, indicated by thelletter S in Fig. 8, both thepump and the motor are hydraulically interlocked by the simple circuit.

. Furthermore,- there is no abrupt change in the and otheradjacentparts. The control assemblage in the housing II is identicalexcept for size, the corresponding parts being designated bycorresponding primed numerals, and dis-' charges through the rod in acorresponding manner with respect to corresponding parts of the motor. I

' In order to operate the pilot-pistons and thereby vary theeccentricity of the pump and motor in a desired relation to each other,a connecting element 90 is secured to the rod 92 of the pilot pistonill, and a threaded rod 9|, in turn, is secured to the connectingelement 99 and received in a suitable bore in the frame '92 of themechanism. A complementarily threaded hand wheel 93 is provided formoving the rod 92 axially to-the desired position. Pivotally mounted inthe connecting element 90 is a coordinating lever 94 which extends toand is pivotally con nected to the operating rod 95.01? the motorcontrol pilot piston. Intermediate the ends of the lever 94 is anelement 96. which is pivotally se cured in the flange 12 on which thehousings-19 and II are mounted, a slot 91-, elongated toward thecontrols, being Provided in the flange I! so that the fulcrum or pivotpoint of theelement 96 may be shifted. By shifting this fulcrum, thedesired relation between the controls may be adjusted for the particularneed. Obviously, as the control rod 82 is drawn outwardly the controlrod 95 for the motor will be correspondingly thrown inwardly, thus anincrease in eccentricity in. either the pump or motor may be accompaniedby a decrease in eccentricity in the other. Thus once having determinedthe 'desired relation and set theffulcrum accordingly, this elationshlpis afterwards'maintained for different speeds by the setting of thesingle hand wheel 93.

tages of the present structure should be noted. As heretofore described,the pump barrel is anti. frictionally mounted in the casing. It is alsoin anti-friction cooperation with the pintle. The crosspins, in turn,-are in anti-friction cooperation with the pistons-and are in rollingoscillat ing engagement with a reactance means which is likewiseanti-frictionally mounted. Thus a completely anti-friction pump isprovided. The

'sameistrue as to each-of the corresponding parts 011 the motor.-,Furthermore, both pump and mot'orare of the same generalcharacteristics,

preferably having the same number of pistons direction of flow of thefluid, delivered by the pump as. it passes directly to the motor and"the discharge pressure of the motor, in turn,

discharges directly to the pump, insuring'complete and instant fillingof the cylinders thereof. Thus a continuous flow through the circuitutilizing the initial flow velocities of the fluid as it leaves the pumpor motor is provided. Due to the anti-friction construction of both thepump and motor, cooling of the fluid by passing itfrom the circuit intoextraneous cooling devices is unnecessary as no-wasteful heat isdeveloped.

Since no wasteful heat is developed, a given speed and setting of themotor and pump will remain constant during long periods of operation.

Since the pump is an entirely anti-friction structure, its. efllciencyremains high regardless, of the stroke, as distinguished from priorstruc-' tures wherein sliding shoes are usedto operate the pistons -orsliding cooperation is provided between-the various parts. In such priorstructures, sliding shoes or other sliding frictional surfaces tend tobind the pump at high pressures and maximum strokes with the result thatthe? total input of power is wasted and utilized only inovercomingfrictional resistances. true for the pump even more true for the motor.Prior structures, none of which are conipletely anti-friction, when usedas a motor-will Y bind and lock frictionally as the short strokeposition isreached. Most such structures, when "used as motors,completelylock at about one fourth stroke.v Once having locked thestatic friction becomes effective and it is impossible .to start themotor again. Consequently all such prior structures have relied upon areversible pump for reversing the operation, but a reversible pumprequired a very complicated fluid circuit. For example, if the stroke ofthe motor should bereduced to about one fourth stroke,

- additional reduction would cause locking or such a great reduction ineiiiciency' that no power .would'be delivered. Thereupon the motor wouldfail to accommodate the delivery ofthe pump and fluid would be entrappedcreating excessive .pressures and vibrations.

Obviously, in such astructure the motor could not 'be adjustedfrom-maximum stroke to zero stroke and. therebeyond in the oppositedirection for' efiecting reversal of the motor. In fact static frictiononce having become effective the only I 80 solution would be to stop thepump and in some Referring next to Figs. 1, 4 and 8, the advantion. Thusinoperation, without any change in the direction of flow of the fluid inthe cirand cooperating in the same manner with the cult, the motor maybe operated at maximum eccentricity or stroke and, whilemaintaining anypredetermined adjustment of the. pump stroke, the motor stroke may bereduced gradually increasing. the speed until the motor stroke is set tozero and during this reduction the motor will accommodate the entireoutput of the pump What is without entrapment of any fiuid until theactual aero stroke position of the motor is reached. At this point-thevalve "51 opens, .,'relieving' the pressure, but immediately uponcontinued movement "of the reactance means of the motor to dispose iteccentrically at the opposite side o! the pintle, the motor will beginoperation in the reverse direction, the valve 51 closing. Therecircuitis in transmission for vehicles because.

of the fact that a'positive but hydraulically elas tic connection isprovidedbetween the power and driven shaft. Safety and emciency'arelikewise provided and the motor can be eflectively used for brakingmerely by setting the pump to neutral. Since both pump and motor are ofthe same general design and completely antifriction, it isapparentthat-either can be used as a pump 'or motor, each being reversible. Thisis necessary for shockless flow of fluid. For

tions in trol means to adjust and set the same ifor effecting differentpredetermined adjusted relations bctweenthe adjustment means consequentupon operation of the said control.

2. Ina hydraulic transmission apparatus of pump rotor and a pistoncarrying motor rotor, each of said rotors having an axial dead end boreand valve ports opening'thereinto, means rotatably mounting said rotorsin the apparatus with said bores coaxial with respect to each other,

the character described having a piston carrying a fixed support in saidapparatus, a stationary valve pintie fixedly mounted intermediate itsend in said support and protruding from its point 3 of connection ateach end, the protruding end example, it the efiiciency 01am motorchanged rapidly, whereas the pumpv remained constant, a.

shock, and pressure rise accompanied by wasteful heat would result.Since both have the same flow characteristics, however,- such effectsare never present.

In the present structure a wide range of starting speed, starting torqueand awide range of static torque and running torque are provided. Thusthe present transmission meets commercial requirements, whereas .a greatreduction in the efiiciency of either the .pump or motor or a' radicalchange in efiiciencies of one with'respect tothe other would render thedevice so inefilcient in regardto range and use that it could notcompete favorably with mechanical transmis- SIODS.

' Due to the great range and speed combinations, great savings in weightand size over mechanical transmissions of comparable range are efiected.Since all parts are of flexibility of argue.

unconnected with the balanced mechanically and hydrostatically, closerfits of the working parts resulting in production of higher pressuresand greater efficiency are obtained. .Finally, due to proper surfacefilm lubrication and use of proper bearings, hardened, high polishedsteel and alioy'parts may be used with such slight clearance that theclearance space between the working faces is sealed by thelubricant,additionally increasing efilciency,

portions of the pintle being coaxial with and received with a hydraulicfit within the respective coaxial bores of the rotors, each end portion.of the pintie having inlet and discharge ports cooperable with theports of the rotors associated therewith,'thepintle havinglongitudinally extending ducts, one communicating with the pintie inletport at the pump end of the pintle'and with a pintie discharge port atthe'motorend of the pintle, the other communicating with a pintiedischarge port at the pump end of the pintie and with a. pintie inletport at the motor end of the pintle, said first mentioned ductextendingthrough the pintle beyond s'aid ports and opening into the dead ends ofboth the rotor and pump bores, and the last mentioned duets being bores.

-3. In a hydraulic transmission apparatus of the character describedhaving a piston carrying ,pump rotor, a piston carrying motor rotor,series to the dead ends of the deadend bores of the rotors respectively,valve ports respective to the pintie end portions positioned forcooperation with the cylinder ports of the respective rotors,.

duct means connecting certain pintle ports of reducing wear, andassuring smo ther and longer operation. I

Having thus des ribed my invenatm, I claim: 1. In a hydraul transmission,echanism including a hydraulic radial piston pump having r a pistoncarrying rotor, pistons reciprocable radially therein, an adiustablereactance means cooperable with the pistons to reciprocate the sameconsequent upon rotation of the rotor, and

a reversible hydraulic radial piston motor having a piston carryingrotor, pistons reciprocable therein, an adjustable reactance meanscooperable with the motor pistons, means respectively for adjustingthe-motor reactance means and the pump reactance means, control meansoperatively connected toboth the motor and pump adjustment means formoving said adjustment means concurrently to different adjusted posioneend with corresponding ports at the other end for passing fluid underoperating pressure therebetween, and said pintie having duct meansopening into the dead end portions of both rotors v and communicatingwith the first mentioned duct means.- i

4. In a hydraulic transmission'apparatus having a pair of radial pistoncarrying rotors, each rotor having an axial dead end bore and aplurality of radial cylinders and each cylinder having a valve portopening into the bore of its respective rotor and means rotatablysupporting the respective rotors with the dead end boresthereoi coaxialand opening toward each other, a stationarypintle, means fixedlysupporting said pintle at a portion intermediate its ends, theprotruding end portions oi. the pintie being co- .axial with andprotruding into the dead end bores of the respective rotors and receivedtherein witi' predetermined relations in respect to each other, andmeans cooperable with the condead ends of the rotor.

portion, said 'pintle terminating at its ends in spaced relation e. fitand terininating in spaced relation' to the dead ends of the boresrespetatively;

valve ports in the protruding portions of the pintle, each end portionof the pintle heving an inlet port and a discharge port cooperablesuccessively with the cylinder ports of the rotor with which it isassociated, consequent upon rotation of such rotor. said pintle having alongitudinally extending pressure .duct connecting the pintle inlet portat the pump end of the pintle with pintleinlet port at the motor end,said suction duct being unconnected with the rotor horesexcept at thevalve ports, and said pressure duct communicating with both the rotorbores at'the dead end portions thereof. h

E'LEK K. BENEDEK.

